Making substantially nonscalloping bimetallic sheet metal



Nov. 13, 1945. w. KEENE ETAL 2,388,694 I MAKING SUBSTANTIALLY NON-SCALLOPING BIMETALLIC SHEET METAL Filed Oct. 3, 1942 N CALLO a AL LOP/N PERCENTAGE REoucr/a/v //v CoLb MILL 1200 1500 1400' 1500 F lN/SH/NG TEMPERTURE OF ROLL/N6 //v HOT MILL DEGREES FAHRENHE/T from directional Patented Nov. 13, 1945 MAKING SUBSTANTIALLY NONSCALLOPING BIMETALLIC SHEET METAL Walter L. Keene, Dormont, Carlson, Pittsburgh, Pa.,

tee] Corporation, tion of Virginia and William A. assignors to Superior Pittsburgh, Pa., a corpora- Application October 3, 1942, Serial No. 460,648 I Claims. (Cl. 148-12) This invention relates to making substantially non-scalloping bimetallic sheet metal. It relates more particularly to a method of making substantially non-scalloping bimetallic sheet metal having a steel component and one or more other components having a relatively low melting point. This application is in part a continuation of our copending application Serial No. 434,342.

Non-scalloping sheet metal is desired for various uses, principally deep drawing. Non-scalloping sheet metal is especially useful in the drawing of ammunition bullet jackets, cartridge cases, etc., where the metal is subjected to severe cold drawing operations. By non-scalloping is meant the quality of drawing uniformly about a die without the formation of the well known objectionable fears." The metal should be of so-called equi-axed" grain structure, substantially free properties.

Bimetal is used for certain of the purposes for which non-scallopingsheet metal is demanded, as, for example, the making of bullet jackets. Bullet Jackets are made of bimetal consisting of a backing oi'steel faced on both sides with a relatively soft corrosion resistant alloy such, for

example, asgilding metal, which consists of in the "neighborhood of 90% copper and in the neighborhood of zinc. It is therefore important to produce substantially non-scalloping bimetal sheet of this type.

It is known that non-scalloping steel can be produced if the steel is hot rolled at such a temperature that the hot rolling is finished while the steel is above the upper critical temperature or Ae3 point. Non-scalloping cold rolled steel such hot rolled steel by cold rolling thehot rolled steel and then annealing the cold rolled steel according to well known practice.

When, however, the melting point of a component employed in making bimetallic sheet is relatively low (e. g., of the order of the melting point of gilding metal, which is in the neighborhood of 1913 F.)- it is not possible to hot roll the bimetal so that the hot rolling is finished before the metal cools below the upper critical temperature of the steel. This is because the hot rolling cannot be commenced with the bimetal at a high enough temperature to insure completion of the hot rolling before its temperature drops below the upper critical temperature of the steel as to do so would necessitate initially heating the bimetal to a temperature above the melting point of the relatively low melting point component, which would result in reducing the relatively low melting point component to molten state in which it obviously could not be rolled. While non-scalloping bimetal can be obtained by normalizing this is sometimes undesirable as it results in increase of the grain size of the nonferrous component.

We have discovered how to make substantially non-scalloping bimetallic sheet metal having a layer of steel and another layer or layers of metal having a relatively low melting point without normalizing. When the melting point of the second mentioned layer or layers (ordinarily the facing) is so low that it is impossible to hot roll the bimetal so that the hot rolling is finished while the metal is at a temperature above the upper critical temperature of the steel it is possible to obtain substantially non-scalloping bimetallic sheet metal by carrying out the rolling in the hot rolling millso that the temperature of the metal at the conclusion of the rolling in such mill is below the upper critical temperature of the steel and following such rolling in the hot rolling mill by rolling in the cold rolling mill to effect at least a predetermined reduction in gauge by such rolling, as will be described below, depending upon the temperature of the metal at the conclusion of the rolling in the hot mill, and then annealing the rolled metal.

Other details, objects and advantages of the invention will become apparent as the following description of a present pre erred method of practicing the same proceeds.

The accompanying drawing consists of a curve showing the relation between the finishing temperature of rolling of bimetallic sheet metal in the hot mill and the minimum percentage of reduction in the cold mill'to which the sheet metal previously rolled in the hot mill should be subjected in order to obtain, after subsequent annealing, substantially non-scalloping bimetallic sheet metal.

The inventionwill be described for purposes of explanation andillustration as employed in the making of bimetallic strip consisting of a component of steel faced on both sides with gilding metal.

The term sheet metal" as used in the claims is intended to comprehend both sheets and strip. In making, for example, bimetallic strip consisting of steel faced on both sides with gilding metal there is first prepared a bimetallic billet having a steel backing and opposed facings of gliding metal secured to the steel backing. This bimetal- -to employ h low carbon steel and that no novelty for 2 lic billet is heated,- rolled in a hot mill, rolled in a cold mill and annealed. It canot be heated to the usual temperature for the hot rolling of steel because the melting temperature of gilding metal is so low that if this were attempted the gilding metal'would melt. Consequently the bimetallic billet must be rolled in the hot mill at temperatures considerably lower than the usual hot rolling temperatures for steel and the finishing temperatureof the work in the hot mill is below the upper critical temperature of steel. For example, the bimetallic billet may be heated to, say, about 1750" F. and the work may be at a temperature of from 1200 to 1500 F. at the conclusion of rolling in the hot mill, depending upon the reduction in gauge desired in the hot mill and other factors encountered in rolling. I

After the work has been rolled in the hot mill it is then rolled in the cold mill. The extent of reduction by rolling in the-cold'mill in relation to the finishing temperature of rolling in the hot mill determineswhether after the subsequent anneal the bimetallic strip will be substantially nonscalloping. The accompanying curve shows the minimum percentage of reduction to which the work should'be subjected in rolling in the cold mill for various finishing temperatures of rolling in the hot mill in order to produce non-scalloping strip. The curve is clear upon its face and needs .no further explanation except that-it is to be mill is above 60%, substantially non-scalloping bimetallic strip will result after the final anneal.

If the finishing temperature of rolling in the hot mill is in the neighborhood of 1300 F. the work should be reduced by rolling in the cold mill at least about 60%. If the finishing temperature of rolling in the hot mill is about 1500 F. the results desired can be obtained by a reduction of at least about 55% in the cold rolling mill.

The meal to which the bimetal rolled as above described is'subiected after completion of rolling in the cold mill is preferably the practice ordinarily followed commercially in annealing low carbon steel. This practice isfof course known to persons skilled inthe art. For a steel having about .1096 carbon a batch anneal in coils at about 1250 to 1300' F. for in the neighborhood of ight hours at temperature is satisfactory. If it is desired to continuously anneal the strip it may bepassedthroughanannealingfurnacemaintained at a temperature'in the neialib hood of 1360 R, each portion of the strip vbeing in the furnace for about four" minutes. rorexample, thestripmaybepassed throughafurnaceabout 32 feetlong at a speed of about eight feet per minute. It is to be understood that we prefer e ordinary commercial anneal for anneal per se is claimed. .The above examples of instead of gliding metal and melting point metals or alloys may be employed comparable results obtained. For example, cupro-nickel or silver may be employed. The melting point of cupronickel having in the neighborhood of 85% c.0p--

per and in the neighborhood of 15% nickel is about 2147 F. The melting point of silver is about 1760 F.

We are aware that some authorities consider the term hot rolling to mean' rolling which is finished while the steel is above the upper critical temperature or Ad point. For this reason and to avoid ambiguity we have not used the expression hot rolling" to describe the rolling of the ,bimetal in a hot mill described and claimed herein since according to our invention the finishing temperature of rollin in the hot mill is below the Ae3 point. Such point for steel containing about .10% carbon is in the neighborhood of 1605 F. Consequently the rolling to which we subject the bimetal in the hot mill may be partly at such a temperature that it would commonly be called hot rolling and is always at least partly below the Ae3 point. The rolling to which we subject the bimetal in the cold mill is always at temperatures below the Au point.

. It is to be understood that the invention is not limited to the particular method above described by way of example and may be otherwise variously practiced within the scope of the following claims.

We claim: 1

l. A method of making substantially non-scalloping bimetallic sheet metal having a layer of steel and a layer of non-ferrous metal having a relatively low melting point comprising heating to a temperature suitable for rolling in a hot rolling mill but below the melting point of the nonferrous metal a bimetallic billet comprising acomponent of steel and a component of said nonferrous metal, rolling said billet into sheet metal in a hot rolling mill, finishing such rolling at a temperature below the upper critical temperature of the steel but not substantially below 1200 FL, rolling the thus rolled sheet metal in a cold rolling mill and thereby reducing its gauge over 60% and annealing the rolled sheet metal.

2. A method of making substantially nonscalloping bimetallic sheet metal having a layer of steel and a layer of non-ferrous metal havinl; a relatively low melting point comprising heating to a temperature suitable for rolling in a hot rolling mill but below the melting point of the nonferrous metal a bimetallic 'billet comprising a of the rolling in the anneals which have been found satisfactory are given purely by way. of illustration.

i The invention is not limited to the making of bimetallic sheet metal in which one oftbe components isgiiding metal. Other relatively low I component of steel and a component of said nonferrous metal, rolling said billet into sheet metal ina hot rolling mill. finishlngsuch rolling at a temperature below the upper critical temperature of the steel, rolling the thus rolled sheet metal in a cold rolling mill and thereby reducing its gauge at'least about the percentage shown on the accompany fl curve for the. finishing temperature hot mill and annealing the rolled sheet metal.

3. A method of making substantially nonscalloping bimetallic sheet metal having a layer'of steel and a layer of non-ferrous metal having a relatively low melting point comprising heating to a temperature suitable for rolling in a hot rolling mill but below the melting point of the non-ferrous metal a bimetallic billet comprising a component of steel and a component of said non-ferrous metal. rolling said billet into sheet metalinahotrollingmimfinishingsuchrolling at a temperature in the neighborhood of 1300 It.

.steel and a layer of'gilding metal comprising heating to a temperature suitable for rolling in a I hot rolling mill but below the melting point of gilding metal a bimetallic billet comprising av component of steel and a component of gliding metal, rolling said billet into sheet metal in a hot rolling mill, finishing such rolling at a temperature below the upper critical temperature of steel, rolling the thus rolled sheet metal in a cold rolling mill and thereby reducing its gauge at least'about the percentage shown on the accompanying curve for the finishing temperature of the rolling in the hot mill and annealing the rolled sheet metal.

. 2,888,894 rolling the thus rolled sheet metal in a cold 5. A method of'making substantially non-scalloping bimetallic sheet metal having a layer of steel and a layer of dissimilar metal whose melting point is so low that it cannot be rolled at usual starting hot rolling temperatures for steel comprising heating to a temperature suitable for roll ing in a hot rolling mill but below the melting point of the dissimilar metal a bimetallic billet comprising a component of steel and a component of dissimilar metal, rolling said billet into sheet metal in a hot rolling mill, finishing such rolling at a temperature below the upper critical temperature of steel, rolling the thus hot rolled sheet metal in a cold rolling mill and thereby reducing its gauge at least about the percentage shown on the accompanying curve for the finishing temperature of the rolling in the hot mill and annealing the rolled sheet metal.

WALTER L. KEENE.

WILLIAM A. CARLSON. 

